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Basics

Basics

Definition

  • Caused by pathogenic members of genus Leptospira.
  • Acute and chronic diseases of dogs (mainly nephritis and hepatitis) and other animals, including, rarely, cats.
  • Dogs-serovars causing disease vary by geographic area; US recent serovars of concern-L. grippotyphosa, L. autumnalis, and L. pomona; vaccines should include representative serovars found in area.

Pathophysiology

  • Leptospira-penetrate intact/cut skin/mucous membranes; rapidly invade bloodstream (4–7 days); spread to all parts of body (2–4 days).
  • Invasion leads to fever, leukocytosis, transitory anemia (hemolysis), mild hemoglobinuria, and albuminuria.
  • Fever and bacteremia soon resolve.
  • Capillary and endothelial cell damage; occasionally results in petechial hemorrhages.
  • Liver-hepatic necrosis and jaundice.
  • Kidney-leptospiruria; Leptospira localize in damaged renal tubules; organism replicates readily in tubular epithelial cell.
  • Early serum antibodies appear about the time bacteremia ceases.
  • Death-usually a result of interstitial nephritis, vascular damage, renal failure; may result from acute septicemia or DIC.

Systems Affected

  • Cardiovascular-endothelial cell damage; hemorrhage
  • Hepatobiliary-hepatitis; dysfunction; necrosis
  • Nervous-meningitis
  • Renal/Urologic-focal interstitial nephritis; hemoglobinuric nephrosis; tubular damage/failure
  • Respiratory-vasculitis; interstitial pneumonia

Chronic Disease

  • Ophthalmic-anterior uveitis
  • Renal/Urologic-chronic renal failure
  • Reproductive-abortion; weak puppies
  • Reproductive-linked to feline stillbirth

Incidence/Prevalence

  • Reported incidence (dogs)-falsely low; most infections are inapparent and remain undiagnosed.
  • Prevalence (dogs)-recent surveys have noted increasing disease in urban dogs; hospital prevalence rates have been increasing since the 1990s.

Geographic Distribution

  • Worldwide, especially in warm, wet climates/seasons.
  • L. canicola and L. icterohaemorrhagiae-usual serovars; clinical disease in dogs; L. canicola most common worldwide; L. icterohaemorrhagiae most common in Australia.
  • L. bratislava-has yet to be confirmed by culture as a serovar in dogs in the United States.
  • Standing water and neutral or slightly alkaline soil promote presence in environment.

Signalment

Species

Dog and rarely cat

Mean Age and Range

  • Young dogs without passive maternal antibody-more likely to exhibit severe disease.
  • Old dogs with adequate antibody titer levels-seldom exhibit clinical disease unless exposed to a serovar not in the vaccine.

Predominant Sex

Traditionally, male dogs more commonly affected; disputed by recent reports.

Signs

General Comments

  • Vary with age/immune status, environmental factors that affect Leptospira survival, and virulence of infecting serovar.
  • Primary reservoir host-may spread particular serovar via urine; may have no clinical signs or less severe disease (acute diffuse to chronic interstitial nephritis, e.g., L. canicola in dogs with relatively weak antibody response).
  • Incidental (accidental) host-acute severe disease (e.g., L. icterohaemorrhagiae in dogs with strong antibody response).

Historical Findings

Peracute to Subacute Disease

  • Fever
  • Sore muscles
  • Stiffness
  • Shivering
  • Weakness
  • Anorexia
  • Depression
  • Vomiting
  • Rapid dehydration
  • Diarrhea:with/without blood
  • Icterus
  • Spontaneous cough
  • Difficulty breathing
  • PU/PD progressing to anuria
  • Bloody vaginal discharge
  • Death-without clinical signs

Chronic Disease

  • No apparent illness
  • Fever of unknown origin
  • PU/PD-chronic renal failure

Physical Examination Findings

Peracute to Acute Disease

  • Tachypnea
  • Rapid irregular pulse
  • Poor capillary perfusion
  • Hematemesis
  • Hematochezia
  • Melena
  • Epistaxis
  • Injected mucous membranes
  • Widespread petechial and ecchymotic hemorrhages
  • Reluctance to move, paraspinal hyperesthesia, stiff gait
  • Conjunctivitis
  • Rhinitis
  • Hematuria
  • Mild lymphadenopathy

Causes

  • Dogs-L. canicola, L. icterohaemorrhagiae, L. pomona, L. grippotyphosa, L. copenhagenii, L. australis, L. autumnalis, L. ballum, and L. bataviae
  • Cats-L. canicola, L. grippotyphosa, L. pomona, and L. bataviae

Risk Factors

Transmission

  • Direct-host-to-host contact via urine, post-abortion discharge, fetus/discharge, sexual contact (semen).
  • Indirect-exposure (via urine) to a contaminated environment (vegetation, soil, food, water, bedding) under conditions in which Leptospira can survive.
  • Disease agent-Leptospira serovar, each with its own virulence factors, infectious dose, and route of exposure.
  • Disease in companion animals is often the result of spillover from diseased wildlife (many different types of mammals) that may be maintenance hosts for different serovars.

Host Factors

  • Vaccine-protection is serovar-specific; may not prevent kidney colonization and urine shedding; new vaccines available of “subunit” type; research has shown promise of panvalent antigen that cross-protects against many serovars.
  • Outdoor animals or hunting dogs-exposure of mucous membranes to water; exposure of abraded or water-softened skin increases risk of infection.

Environmental Factors

  • Warm and moist environment; wet season (high rainfall areas) of temperate regions; low-lying areas (marshy, muddy, irrigated); warm humid climates of tropical and subtropical regions.
  • Temperature range-7–10°C (44.6–50°F) to 34–36°C (93–96°F).
  • Water-organism survives better in stagnant than flowing water; in neutral or slightly alkaline pH.
  • Organism survives 180 days in wet soil and longer in standing water.
  • Dense animal population-kennels/urban settings; increases chances of urine exposure.
  • Exposure to rodents and other wildlife.

Diagnosis

Diagnosis

Differential Diagnosis

Subacute to Acute Disease

  • Dogs-heartworm disease; immune-mediated hemolytic anemia; bacteremia/septicemia; infectious canine hepatitis virus; canine herpesvirus; hepatic neoplasia; trauma; lupus; Rocky Mountain spotted fever; ehrlichiosis; toxoplasmosis; renal neoplasia; renal calculi.
  • Cats-hemotrophic mycoplasmosis; drugs (acetaminophen); bacteremia/septicemia; FIV- and FeLV-associated diseases; cholangitis; toxoplasmosis; FIP; hepatic neoplasia; autoimmune disease; trauma; renal calculi; renal neoplasia.

Reproductive/Neonatal Disease

  • Dogs-brucellosis; distemper; herpes.
  • Cats-FIP; FeLV; panleukopenia; herpesvirus; toxoplasmosis; salmonellosis.

CBC/Biochemistry/Urinalysis

  • PCV and total plasma solids-high owing to dehydration; rarely PCV low (hemolysis)
  • Leukocytosis with left shift-leukopenia initially during leptospiremic phase
  • Thrombocytopenia
  • Increased fibrin degradation products
  • BUN and creatinine-high; mainly renal
  • Electrolyte alterations-depend on degree of renal and gastrointestinal dysfunction
  • Hyponatremia
  • Hypochloremia
  • Hypokalemia-hyperkalemia with kidney failure
  • Hyperphosphatemia
  • Hypoalbuminemia
  • Acidosis-serum bicarbonate low
  • Alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, alkaline phosphatase-high
  • Proteinuria
  • Isosthenuria-acute renal failure

Other Laboratory Tests

Serology (Microscopic Agglutination Test)

  • Test serum in acute stage and also 3–4 weeks later (convalescent)
  • Unvaccinated patients-titers may be low initially (1:100–1:200); may be higher in the convalescent serum (1:800–1:1,600 or higher) if a homologous Leptospira serovar is tested; several serovars may cross-react in the MAT test, especially if there are high titers to a single serovar.
  • Vaccinated patients, older whole cell bacteria-expect high titers (for up to 12–16 weeks post-vaccination), then drop off to <1:400; new subunit vaccines-titers rise to 1:1,600 for 12 weeks for serovars L. canicola and L. icterohaemorrhagiae; titers for other subunit vaccine serovars are more variable (L. pomona and L. grippotyphosa).
  • Run all serum samples (acute and convalescent) at the same time, if possible.

Darkfield Microscopy of Urine

  • Often inconclusive
  • Difficult to read
  • Requires fresh urine

Fluorescent Antibody Test of Urine

  • More conclusive.
  • Leptospira not need to be viable; submit urine to lab on ice by overnight courier.
  • Pretreat with furosemide 15 minutes before urine collection to increase success rate.
  • Correlate results with clinical history.

PCR Test of Urine and Tissue

  • Promising but still experimental

Diagnostic Procedures

  • Culture of body fluids antemortem (urine, blood, aqueous humor) and tissues post-mortem (kidney, liver, fetus, placenta)-usually not practical due to fastidiousness of Leptospiras; contact laboratory for the proper transport medium.
  • Fluorescent antibody test-done on tissues submitted for post-mortem workup, especially kidney and liver.
  • Special stains (Warthin-Starry silver)-attempt immunohistochemistry with monoclonal antibodies on formalin-fixed sections of kidney, liver, and fetal/placental tissue.
  • PCR-some labs have protocols for urine/tissue specimens.

Pathologic Findings

  • Degree of kidney and liver disease depends on serovar and the host's immunity.
  • Cats-generally less severe lesions.
  • Dogs (acute disease)-lungs may be edematous; kidneys pale and enlarged; liver enlarged, may be friable with multifocal necrosis/hemorrhage; gastrointestinal tract may hemorrhage.

Treatment

Treatment

Nursing Care

  • Dehydration and shock-parenteral, balanced, polyionic, isotonic intravenous solution (lactated Ringer's).
  • Severe hemorrhage-blood transfusion may be needed in association with treatment for DIC.
  • Oliguria or anuria-initially rehydrate; then give intravenous osmotic diuretics or tubular diuretics; peritoneal dialysis may be necessary.

Client Education

Inform client of zoonotic potential from contaminated urine of affected dogs and their environment.

Medications

Medications

Drug(s) Of Choice

  • Procaine penicillin G 40,000–80,000 U/kg IM q24h or divided q12h until kidney function returns to normal.
  • Dihydrostreptomycin-10–15 mg/kg IM q12h for 2 weeks to eliminate organism from kidney interstitial tissues; try streptomycin if no renal failure; drug not available everywhere.
  • Doxycycline 5 mg/kg PO or IV q12h for 3 weeks; use alone to clear both leptospiremia and leptospiruria.

Precautions

  • Aminoglycoside-carefully monitor patients with renal insufficiency.
  • Penicillins (dogs)-adjust doses with renal insufficiency.

Alternative Drug(s)

  • Ampicillin or amoxicillin-instead of penicillin (ampicillin 22 mg/kg PO q6–8h for 3 weeks; amoxicillin (22 mg/kg PO q8–12h for 3 weeks).
  • Azithromycin-20 mg/kg PO q24h for 3 weeks.

Follow-Up

Follow-Up

Prevention/Avoidance

  • Vaccine (dogs)-whole cell bacterin vaccines contain serovars L. canicola/icterohaemorrhagiae (newer also include L. pomona/grippotyphosa); promotes immunity to homologous serovars and protection from overt clinical disease; may not prevent colonization of the kidneys, resulting in chronic carrier state; serovar-specific; does not promote protection against other serovars present in nature. Newer subunit vaccine contains L. pomona, L. icterohaemorrhagiae, L. grippotyphosa, and L. canicola; claims made that subunit provides protection from clinical disease/prevents kidney colonization.
  • Vaccines-vaccinate dogs per current label recommendations; bacteria-induced immunity lasts only 6–8 months and is serovar-specific (no cross-protection outside of the serogroup); revaccinate at least yearly; vaccinate high-risk dogs (hunter, show dogs, dogs with access to water/ponds) every 4–6 months, especially in endemic areas.
  • Kennels-strict sanitation to avoid contact with infected urine; control rodents; monitor/remove carrier dogs until treated; isolate infected animals during treatment.
  • Activity-limit access to marshy/muddy areas, ponds, low-lying areas with stagnant surface water, heavily irrigated pastures, access to wildlife.
  • Environmental contamination: Leptospira shedding in urine is intermittent; Leptospira survive in urine in the environment but do not multiply; cells survive until either drying, UV light exposure or freeze-thaw has killed the Leptospira.

Possible Complications

  • DIC
  • Permanent liver/kidney dysfunction
  • Uveitis
  • Abortion

Expected Course and Prognosis

  • Most infections subclinical or chronic
  • Prognosis guarded for acute severe disease

Miscellaneous

Miscellaneous

Age-Related Factors

Severe clinical disease in young dogs (non-vaccinated or lacking maternal antibody)

Zoonotic Potential

  • High; spread in urine of infected animals.
  • Strict kennel hygiene and disinfection of premises (iodine-based disinfectant or stabilized bleach solutions).
  • Acutely infected and carrier animals must be treated.

Pregnancy/Fertility/Breeding

  • Possible abortion.
  • Antimicrobial therapy-consider effect of drug on developing fetus.

Abbreviations

  • DIC = disseminated intravascular coagulation
  • FeLV = feline leukemia virus
  • FIP = feline infectious peritonitis
  • FIV = feline immunodeficiency virus
  • PCR = polymerase chain reaction
  • PCV = packed cell volume
  • PU/PD = polyuria/polydipsia

Internet Resources

http://www.cfsph.iastate.edu/DiseaseInfo/disease.php?name=leptospirosis&lang=en

Author Patrick L. McDonough

Consulting Editor Stephen C. Barr

Client Education Handout Available Online